GEARED UNISON RING FOR VARIABLE VANE ACTUATION
An actuator system including a harmonic drive operable to drive a variable vane system of a gas turbine engine.
The present disclosure relates to a gas turbine engine and, more particularly, to a variable vane system therefor.
Gas turbine engines, such as those that power modern commercial and military aircraft, generally include a compressor section to pressurize an airflow, a combustor section to burn a hydrocarbon fuel in the presence of the pressurized air, and a turbine section to extract energy from the resultant combustion gases.
Some gas turbine engines include variable vanes that can be pivoted about their individual axes to change an operational performance characteristic. Typically, the variable vanes are robustly designed to handle the stress loads that are applied to change the position of the vanes. A mechanical linkage is typically utilized to rotate the variable vanes. Because forces on the variable vanes can be relatively significant, forces transmitted through the mechanical linkage can also be relatively significant. Legacy compressor designs typically utilize fueldraulic actuation to rotate the variable vanes.
SUMMARYA variable vane system according to one disclosed non-limiting embodiment of the present disclosure can include an actuator; a harmonic drive driven by the actuator; a drive gear driven by the harmonic drive; a geared unison ring driven by the drive gear; and an actuator gear mounted to a variable vane, the actuator gear driven by the extended geared unison ring.
A further embodiment of the present disclosure may include an actuator gear mounted to each of a multiple of variable vane.
A further embodiment of the present disclosure may include wherein the unison ring includes a first gear rack meshed with the actuator gear.
A further embodiment of the present disclosure may include wherein the unison ring includes a gear rack segment meshed with the drive gear.
A further embodiment of the present disclosure may include wherein the harmonic drive includes a strain wave gearing mechanism.
A further embodiment of the present disclosure may include wherein the strain wave gearing mechanism include a fixed circular spline, a flex spline attached to an output shaft, and a wave generator attached to an input shaft, the flex spline driven by the wave generator with respect to the circular spline.
A further embodiment of the present disclosure may include wherein the harmonic drive provides between a 30:1-320:1 gear ratio.
A further embodiment of the present disclosure may include wherein the actuator gear is a gear segment.
A further embodiment of the present disclosure may include wherein the actuator gear is operable to rotate through about 90 degrees.
A further embodiment of the present disclosure may include wherein the actuator gear is operable to rotate through about 0-40 degrees.
A further embodiment of the present disclosure may include wherein the actuator gear is mounted to a trunion of a variable vane.
A further embodiment of the present disclosure may include wherein the geared unison ring includes an interface with an engine case of a gas turbine engine to restrain axial motion.
A gas turbine engine according to one disclosed non-limiting embodiment of the present disclosure can include a harmonic drive operable to drive a variable vane system through a geared unison ring.
A further embodiment of the present disclosure may include wherein the geared unison ring operable to drive a multiple of variable vanes, the geared connection operable to drive the unison ring.
A further embodiment of the present disclosure may include wherein the unison ring includes a first gear rack meshed with the actuator gear.
A further embodiment of the present disclosure may include wherein the unison ring includes a gear rack segment meshed with the drive gear.
A further embodiment of the present disclosure may include wherein the geared unison ring includes an interface with an engine case of a gas turbine engine to restrain axial motion.
The foregoing features and elements may be combined in various combinations without exclusivity, unless expressly indicated otherwise. These features and elements as well as the operation thereof will become more apparent in light of the following description and the accompanying drawings. It should be appreciated; however, the following description and drawings are intended to be exemplary in nature and non-limiting.
Various features will become apparent to those skilled in the art from the following detailed description of the disclosed non-limiting embodiment. The drawings that accompany the detailed description can be briefly described as follows:
The engine 20 generally includes a low spool 30 and a high spool 32 mounted for rotation about an engine central longitudinal axis A relative to an engine static structure 36 via several bearing compartments 38. The low spool 30 generally includes an inner shaft 40 that interconnects a fan 42, a low pressure compressor 44 (“LPC”) and a low pressure turbine 46 (“LPT”). The inner shaft 40 drives the fan 42 directly or thru a geared architecture 48 to drive the fan 42 at a lower speed than the low spool 30. An exemplary reduction transmission is an epicyclic transmission, namely a planetary or star gear system.
The high spool 32 includes an outer shaft 50 that interconnects a high pressure compressor 52 (“HPC”) and high pressure turbine 54 (“HPT”). A combustor 56 is arranged between the HPC 52 and the HPT 54. The inner shaft 40 and the outer shaft 50 are concentric and rotate about the engine central longitudinal axis A which is collinear with their longitudinal axes.
Core airflow is compressed by the LPC 44 then the HPC 52, mixed with fuel and burned in the combustor 56, then expanded over the HPT 54 and the LPT 46. The turbines 54, 46 rotationally drive the respective low spool 30 and high spool 32 in response to the expansion. The main engine shafts 40, 50 are supported at a plurality of points by the bearing compartments 38. It should be understood that various bearing compartments 38 at various locations may alternatively or additionally be provided.
In one example, the gas turbine engine 20 is a high-bypass geared aircraft engine with a bypass ratio greater than about six (6:1). The geared architecture 48 can include an epicyclic gear train, such as a planetary gear system or other gear system. The example epicyclic gear train has a gear reduction ratio of greater than about 2.3:1, and in another example is greater than about 3.0:1. The geared turbofan enables operation of the low spool 30 at higher speeds which can increase the operational efficiency of the LPC 44 and LPT 46 to render increased pressure in a relatively few number of stages.
A pressure ratio associated with the LPT 46 is pressure measured prior to the inlet of the LPT 46 as related to the pressure at the outlet of the LPT 46 prior to an exhaust nozzle of the gas turbine engine 20. In one non-limiting embodiment, the bypass ratio of the gas turbine engine 20 is greater than about ten (10:1), the fan diameter is significantly larger than that of the LPC 44, and the LPT 46 has a pressure ratio that is greater than about five (5:1). It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine and that the present disclosure is applicable to other gas turbine engines including direct drive turbofans, where the rotational speed of the fan 42 is the same (1:1) of the LPC 44.
In one example, a significant amount of thrust is provided by the bypass flow path due to the high bypass ratio. The fan section 22 of the gas turbine engine 20 is designed for a particular flight condition—typically cruise at about 0.8 Mach and about 35,000 feet (10668 meters). This flight condition, with the gas turbine engine 20 at its best fuel consumption, is also known as bucket cruise Thrust Specific Fuel Consumption (TSFC). TSFC is an industry standard parameter of fuel consumption per unit of thrust.
Fan Pressure Ratio is the pressure ratio across a blade of the fan section 22 without the use of a Fan Exit Guide Vane system. The relatively low Fan Pressure Ratio according to one example gas turbine engine 20 is less than 1.45. Low Corrected Fan Tip Speed is the actual fan tip speed divided by an industry standard temperature correction of (“T”/518.7)0.5 in which “T” represents the ambient temperature in degrees Rankine. The Low Corrected Fan Tip Speed according to one example gas turbine engine 20 is less than about 1150 fps (351 m/s).
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The variable vane system 100 may include a plurality of variable vanes 102 circumferentially arranged around the engine central axis A. The variable vanes 102 each include a variable vane body that has an airfoil portion that provides a lift force via Bernoulli's principle such that one side of the airfoil portion generally operates as a suction side and the opposing side of the airfoil portion generally operates as a pressure side. Each of the variable vanes 102 generally spans between an inner diameter and an outer diameter relative to the engine central axis A.
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The variable vane system 100 is driven by an actuator system 118 with an actuator 120, a harmonic drive 122 and an actuator arm 124. Although particular components are separately described, it should be appreciated that alternative or additional components may be provided. Although a single actuator system 118 may be utilized for each stage (
The actuator 120 may include an electric motor or other electric powered device. The actuator 120 is defined along an axis B.
The harmonic drive 122 includes a strain wave gearing mechanism 130 that, in one example, may provide a 30:1-320:1 gear ratio in a compact package that significantly reduces the rotation and increases the torque provided by the actuator 120. The strain wave gearing mechanism 130 generally includes a fixed circular spline 132, a flex spline 134 attached to an output shaft 136 along an axis B, and a wave generator 138 attached to an input shaft 140 which is connected to the actuator 120 along axis B (
The harmonic drive 122 essentially provides no backlash, compactness and light weight, high gear ratios, reconfigurable ratios within a standard housing, good resolution and excellent repeatability when repositioning inertial loads, high torque capability, and coaxial input and output shafts. The harmonic drive 122 thereby prevents back driving by the relatively high aerodynamic forces experienced by the variable vanes 102.
The harmonic drive 122 need only rotate the drive arm 124 through about 90 degrees and, in a more specific embodiment, only about 0-40 degrees to drive rotation of the unison ring 110, thence the individual variable vanes 102 through the respective drive arms 112. That is, the actuator arm 124 rotates the unison ring 110 that, in turn, rotates the drive arms 112 along their respective axis D to rotate the trunions 106, and thus the variable vanes 102 about axis V.
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The other variable vanes 102 are attached to the unison ring 110 though respective links 146. The geared connection 140 provides for an offset to accommodate insufficient space for a direct connection attached concentric to the axis of a variable vane, such as the first LPC variable vane stage that is typically adjacent to a structural wall 148 such as a firewall (
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The first plane 204 and the second plane 208 are offset such that the first set of gear teeth 202 are in mesh with a first drive gear 210 for a drive variable vane 102 in a first stage 212 and the second set of gear teeth 206 in mesh with a second drive gear 214 for a drive variable vane 102 in a second stage 216. The first drive gear 210 and the second drive gear 214 may be arranged at different heights to interface with the multi-planar gear 200. Since actuation requires only partial rotation, symmetry of the multi-planar gear 200 is not necessary. The gear ratio can be adjusted to provide different vane rotations per stage.
The first drive gear 210 and the second drive gear 214 also include a drive arm 218, 220 to rotate a respective unison ring 222, 224. The driven variable vanes 102 are connected their respective unison ring 222, 224 by a respective linkage 226,228 for each variable vane 102.
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In this embodiment, a multi-planar gear 232 may be driven by a drive shaft 240 driven by a remote actuator.
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Rotation of the geared unison ring 260 by the actuator system 118F drives the individual variable vanes 102 through the respective drive arms 204. The actuator system 118F is generally axial with the engine axis A for installations with limited vertical packaging space. The actuator system 118F drives a drive gear 264 that is wider than the gear 262 as the rotation of the unison ring 260 results in a relatively small amount of axial motion (
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The groove 284 defines a contoured path to guide the cable 286 (
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Alternatively, an additional actuation arm 380 may extend from the vane drive bevel gear 382 to provide the same linkage motion to the unison ring 384 as the actuation arms on the variable vanes, but is aligned to the bevel gear 382. The unison ring 384 may include a bridge 386 which bridges a subset of a multiple of variable vane drive arms 388. That is, the bridge 386 is mounted to the unison ring 384 to which the multiple of variable vane drive arms 388 are attached. The actuation arm 380, since not tied directly to a variable vane, is mounted to static structure 390.
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The gearbox 404 may house all the necessary supports and bearings and may be mounted directly to the engine case 406 such as a HPC case. The gearbox 404 also provides a static structure from which to rotationally mount the variable vane actuation arms 420, 422 that are not tied directly to a variable vane 418, 424. The variable vane actuation arms 420, 422 may be mounted to a bridge 424, 426 that is mounted to the respective unison ring 428, 430.
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The actuator system 118J permits variable vane stages to be actuated independently from a remote distance to provide thermal isolation behind a firewall, or because the motors must be relocated due to limited packaging space.
Although the different non-limiting embodiments have specific illustrated components, the embodiments of this invention are not limited to those particular combinations. It is possible to use some of the components or features from any of the non-limiting embodiments in combination with features or components from any of the other non-limiting embodiments.
It should be understood that relative positional terms such as “forward,” “aft,” “upper,” “lower,” “above,” “below,” and the like are with reference to the normal operational attitude of the vehicle and should not be considered otherwise limiting.
It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings. It should also be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom.
Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present disclosure.
The foregoing description is exemplary rather than defined by the limitations within. Various non-limiting embodiments are disclosed herein, however, one of ordinary skill in the art would recognize that various modifications and variations in light of the above teachings will fall within the scope of the appended claims. It is therefore to be understood that within the scope of the appended claims, the disclosure may be practiced other than as specifically described. For that reason the appended claims should be studied to determine true scope and content.
Claims
1. A variable vane system, comprising:
- an actuator;
- a harmonic drive driven by the actuator;
- a drive gear driven by the harmonic drive;
- a geared unison ring driven by the drive gear; and
- an actuator gear mounted to a variable vane, the actuator gear driven by the extended geared unison ring.
2. The system as recited in claim 1, further comprising an actuator gear mounted to each of a multiple of variable vane.
3. The system as recited in claim 1, wherein the unison ring includes a first gear rack meshed with the actuator gear.
4. The system as recited in claim 3, wherein the unison ring includes a gear rack segment meshed with the drive gear.
5. The system as recited in claim 1, wherein the harmonic drive includes a strain wave gearing mechanism.
6. The system as recited in claim 5, wherein the strain wave gearing mechanism include a fixed circular spline, a flex spline attached to an output shaft, and a wave generator attached to an input shaft, the flex spline driven by the wave generator with respect to the circular spline.
7. The system as recited in claim 1, wherein the harmonic drive provides between a 30:1-320:1 gear ratio.
8. The system as recited in claim 1, wherein the actuator gear is a gear segment.
9. The system as recited in claim 8, wherein the actuator gear is operable to rotate through about 90 degrees.
10. The system as recited in claim 8, wherein the actuator gear is operable to rotate through about 0-40 degrees.
11. The system as recited in claim 1, wherein the actuator gear is mounted to a trunion of a variable vane.
12. The system as recited in claim 1, wherein the geared unison ring includes an interface with an engine case of a gas turbine engine to restrain axial motion.
13. A gas turbine engine, comprising:
- a harmonic drive operable to drive a variable vane system through a geared unison ring.
14. The gas turbine engine as recited in claim 14, wherein the geared unison ring operable to drive a multiple of variable vanes, the geared connection operable to drive the unison ring.
15. The gas turbine engine as recited in claim 13, wherein the unison ring includes a first gear rack meshed with the actuator gear.
16. The gas turbine engine as recited in claim 15, wherein the unison ring includes a gear rack segment meshed with the drive gear.
17. The gas turbine engine as recited in claim 13, wherein the geared unison ring includes an interface with an engine case of a gas turbine engine to restrain axial motion.
Type: Application
Filed: Mar 24, 2016
Publication Date: Sep 28, 2017
Patent Grant number: 10294813
Inventors: Anthony R. Bifulco (Ellington, CT), Gabriel L. Suciu (Glastonbury, CT), Jesse M. Chandler (South Windsor, CT)
Application Number: 15/079,505